Strip metal stamping and forming operations are widely used to produce articles such as fasteners or electrical terminals in continuous strip form. The commonly known type of forming apparatus comprises a press having a C-shaped frame member and a progressive die assembly mounted in the press. The die assembly has upper and lower die shoes, the upper shoe being reciprocated towards the lower shoe by a ram in the upper arm of the press which in turn is continuously reciprocated by a crank or eccentric. A feeding mechanism intermittently feeds the strip material through the press and between the upper and lower die shoes which contain a plurality of individual die stations. Each station will contain complementary upper and lower tooling for carrying out the operations which are performed on the material as it is fed through the die assembly, for example, a blanking or profiling operation which may be followed by several punching and forming operations during which individual articles are formed from the strip.
Stamping presses as described above are widely used and have been used ever since continuous stamping became an efficient manufacturing process. The equipment presently used for such operations has been satisfactory in the past and is highly reliable, however, presently used equipment has many shortcomings and disadvantages which must be contended with in present day strip manufacturing operations. For example, many of the parts made by stamping such as electrical terminals or fasteners are quite small and are produced from strip material having a thickness of 0.015 inches or less. However, the presses used for the forming operations are relatively massive and would appear to be greatly oversized relative to the scale of the operations being carried out. In fact, relatively massive presses and die shoe assemblies are required because the loading of the parts of the press is eccentric or non-symmetrical and the parts, such as the frame casting, must be enlarged so that they will be able to withstand the eccentric loading during millions of cycles of operation.
Because of the relatively high masses of the parts, presses now used for stamping and forming operations produce a very high level of noise in the work place and increasingly, it is becoming necessary to take steps to reduce the level of noise for reasons of the health of the workers.
The stroke of most presses used for high speed stamping and forming operations is extremely long relative to the nature of the operations being performed on the strip material; in other words, the stroke of the press will frequently have many times the maximum lateral dimension of the part being produced. As a result of the fact that the stroke is unduly long, the inertia developed during ech cycle is relatively high and the linear speed of the press ram is very high, particularly if the press is operated at a high speed, say 500 strokes per minute. These factors result in unduly high power requirements for the press and in the imposition of unduly high stresses in the tooling and other parts which are subject to wear. As a result, the maintenance costs for the tooling are increased, particularly if the press is being used to produce precisely dimensioned parts such as electrical terminals.
The present invention is directed to the achievement of an improved machine for performing stamping and forming, or similar, operations on strip material which will overcome the shortcomings of existing stamping presses. The invention is thus directed to the achievement of a machine which has greatly reduced power requirements, which will be extremely quiet as compared with existing stamping and forming machines, which can be operated at extremely high speeds without accompanying excessive wear of the press parts or the forming tooling and which can be "set up" or modified for different parts in a minimum amount of time. The invention is further directed to the achievement of a machine which does not require a conventional progressive die assembly but which is nonetheless capable of carrying out all of the stamping and forming operations which are now carried out by means of progressive dies.
One embodiment of the invention comprises a machine module for performing operations on strip material of the type comprising a strip feeder for intermittently feeding the material in a vertical plane along a strip feed path, an operating zone on the strip feed path, and first and second opposed tool holders in the operating zone. The tool holders are on opposite sides of the strip feed path and are reciprocable between retracted positions, in which the tool holders are relatively remote from the strip feed path, and closed positions, in which the tool holders are proximate to the strip feed path. The machine has actuating means for actuating the strip feeder and for reciprocating the tool holders in timed sequence with actuation of the strip feeder so that the tool holders arrive at, and depart from, their closed positions during dwell of the strip. The machine is characterized in that the actuating means comprises a continuously rotatable power shaft, first and second actuator levers, and first and second connecting links. The power shaft extends parallel to, and is spaced from, the strip feed path in the operating zone. The strip feed path and the vertical diametral plane of the power shaft lie in a common plane. The first and second actuator levers are on opposite sides of the common plane, the actuator levers being pivoted on first and second pivotal axes which extend parallel to the axis of the power shaft. The first and second connecting links are pivotally connected at one end to the first and second actuator levers and are eccentrically coupled at the other end to the power shaft. Coupling means are provided for coupling the first and second actuator levers to the tool holders. During continuous rotation of the power shaft, the actuator levers are oscillated by the connecting links and the tool holders are reciprocated by the actuator levers.
In accordance with a further embodiment, the strip feeder is located between the strip feed path and the power shaft, the first and second actuator levers are co-planar, and the first and second actuator levers and the first and second connecting links are symmetrical with respect to the common plane. The first and second actuator levers are substantially identical in mass and moment of inertia, the first and second connectng links are substantially identical in mass and moment of inertia, and the strokes of the first and second tool holders are the same whereby the machine is balanced with respect to the common plane.
In accordance with a further embodiment, a plurality of modules as described above are mounted on a machine bed and the strip material is fed through the modules and an operation is performed on the strip in each module. The modules are preferably adjustably mounted on the machine bed so that any lengthening of the strip which may take place as a result of the operations performed can be accommodated.